/Engine/Plugins/Runtime/GameplayAbilities/Source/GameplayAbilities/Public/GameplayEffect.h
Returns the magnitude of a SetByCaller modifier. Will return 0.f and Warn if the magnitude has not been set.
float GetSetByCallerMagnitude ( [FName](API\Runtime\Core\UObject\FName) DataName, bool WarnIfNotFound, float DefaultIfNotFound ) const